This invention relates to an accumulator-dehydrator assembly for an air conditioning system. This invention specifically relates to an accumulator-dehydrator that eliminates the traditional J-shaped tube inside the accumulator-dehydrator and replaces the J-shaped tube with an inline trumpet tube which will not fill up with liquid and which utilizes an oil siphoning system to provide oil return to the compressor.
Vehicle air conditioning systems include a compressor that compresses and superheats refrigerant, which then runs through a condenser, expander and evaporator in turn before returning to the compressor to begin the cycle again. Entrained within the refrigerant is a small amount of lubricating oil, which is needed to ensure smooth performance and prolong the life of the compressor.
Interposed between the evaporator and compressor is an accumulator-dehydrator which is designed to accomplish several objectives. The accumulator-dehydrator primarily receives and accumulates the evaporator effluent. The evaporator effluent typically includes both a liquid component and a vapor component. The accumulator-dehydrator serves as a reservoir or separator in which liquid collects at the bottom of the reservoir and vapor collects at the top. The accumulator-dehydrator ensures that only refrigerant in a vapor stage passes to the compressor. The accumulator-dehydrator also prevents a liquid slug from being pulled or sucked into the compressor. Still further, a desiccant is typically located in the bottom of the accumulator-dehydrator to absorb any water in the refrigerant.
Traditionally accumulator-dehydrators are known to use a U-shaped or J-shaped tube more commonly known as a J-tube. The accumulator-dehydrator is fundamentally a canister with inlet and outlet fittings. The inlet fitting is connected to the evaporator. The refrigerant enters the inlet as a vapor and liquid mixture. The liquid drops to the bottom of the canister and the vapor rises to the top. The J-tube is connected at one end to the canister outlet, which in turn is connected to the compressor. The J-tube extends down from the outlet to adjacent the bottom of the canister and then turns upward and extends to adjacent the top of the canister. The free end of the J-tube, the portion near the canister top, is open to allow the refrigerant vapor to be drawn into the J-tube and exit through the outlet fitting to the compressor. A small opening is provided in the bottom turn-portion or U-portion of the J-tube to allow the liquid including the oil, to enter the J-tube and be entrained and delivered with the refrigerant vapor to the compressor.
With traditional J-tube accumulator-dehydrators and the compressor disengaged (no flow through the J-tube), the J-tube will fill with liquid to the same level as the liquid in the canister. When the compressor is engaged a large pressure differential quickly occurs across the liquid stored in the J-tube. This large pressure differential causes the liquid in the J-tube to accelerate rapidly and to violently boil off. This rapid liquid acceleration and boiling imparts energy to the accumulator-dehydrator, which is classified as xe2x80x9cbumpxe2x80x9d energy. This xe2x80x9cbumpxe2x80x9d energy is present in all traditional J-tube accumulator-dehydrators. This energy manifests itself as a broad frequency noise known as the xe2x80x9cbumpxe2x80x9d.
The energy imparted to the accumulator-dehydrator is a function of the rate of pressure drop across the liquid level in the J-tube within the accumulator-dehydrator and the amount of liquid in the J-tube. The pressure drop is affected by the compressor displacement, compressor drive ratio, and the amount of internal volume on the suction side of the accumulator-dehydrator. The magnitude and occurrence of noise is dependent on the total energy imparted to the accumulator-dehydrator, and the extent of accumulator-dehydrator isolation. All noise is unpleasant to the occupants of the vehicle. A smoother running and quieter air conditioning system is much more appealing to the occupants. This bump energy and the associated noise occur to some degree in all current J-tube accumulator-dehydrators.
Some attempts have been made to try to eliminate this bump energy by eliminating the traditional J-tube that fills with liquid. An example of an accumulator-dehydrator eliminating the traditional J-tube and replacing the traditional J-tube with a tube that does not fill with liquid is shown in U.S. Pat. No. 4,331,001. In this system, the traditional J-tube is replaced with an extended outlet fitting mounted within a desiccant. In this system all of the vapor in the accumulator-dehydrator is pulled through the desiccant. Because of the amount of suction required to pull the vapor through the desiccant there is a very large pressure drop across the accumulator-dehydrator. The large pressure drop that occurs makes the accumulator-dehydrator inefficient as well as making the entire air conditioning system less efficient, which can lead, to decreased life of the air conditioning components. This unit also is a more complicated design with additional parts, making the unit more expensive to manufacture.
The accumulator-dehydrator of the present invention contains an inline trumpet tube that does not fill with liquid while the compressor is disengaged. The inline trumpet tube may or may not have a pressure equalization hole (PEH) through the wall of the trumpet tube and a restricted flow diameter in the middle of the tube. Attached to the bottom of the inline trumpet tube is an oil pick up tube with the restricted flow diameter at the location where the oil pick up tube attaches to the trumpet tube. The restricted flow diameter produces a venturi effect that is designed to create a pressure differential across the oil pick up tube. This pressure differential drives a small portion of the oil and refrigerant liquid from the bottom of the canister, up through the pick up tube, and into the outlet vapor flow. This small portion of liquid provides lubrication and cooling for the compressor. At the bottom of the oil pick up tube is a filter. The inline trumpet tube also contains an anti-siphon feature through the use of the PEH (pressure equalization hole). The PEH equalizes the pressure in the trumpet tube with that in the canister. This insures that if liquid does accumulate in the trumpet tube, it will not be pulled into the compressor by refrigerant migration. Refrigerant migration occurs while the compressor is disengaged or off. In the preferred embodiment, the inline trumpet tube has a trumpet shaped end, which is flared to at least 30 degrees with respect to vertical as illustrated in FIG. 1. This trumpet shaped end opens upwards towards the top of the canister.
Because the vapor portions of the refrigerant and oil do not have to be pulled through the desiccant, nor through the U-shaped portion of the current J-tube, the pressure drop is significantly decreased. This design also allows the accumulator-dehydrator to work much more efficiently because of reduced pressure drop and therefore the entire air conditioning system performs more efficiently.